import os
import base64
import requests
import io
from PIL import Image
from pypdf import PdfReader

NVIDIA_API_KEY = os.environ.get("NVIDIA_API_KEY", "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")

NEMOTRON_OCR_V2_URL = "https://ai.api.nvidia.com/v1/cv/nvidia/nemotron-ocr-v2"
NEMOTRON_OCR_V1_URL = "https://ai.api.nvidia.com/v1/cv/nvidia/nemotron-ocr-v1"

def process_image_for_ocr(image_path: str, max_b64_len: int = 175000) -> str:
    """
    Reads image file, resizes if necessary to ensure Base64 string is under NVIDIA 180KB payload limit.
    """
    with Image.open(image_path) as img:
        img = img.convert("RGB")
        buf = io.BytesIO()
        img.save(buf, format="JPEG", quality=85)
        b64_str = base64.b64encode(buf.getvalue()).decode()
        
        scale = 0.9
        while len(b64_str) > max_b64_len and scale > 0.2:
            new_w = int(img.width * scale)
            new_h = int(img.height * scale)
            resized_img = img.resize((new_w, new_h), Image.Resampling.LANCZOS)
            buf = io.BytesIO()
            resized_img.save(buf, format="JPEG", quality=80)
            b64_str = base64.b64encode(buf.getvalue()).decode()
            scale -= 0.1
            
        return b64_str

def extract_pdf_text_and_pages(pdf_path: str) -> dict:
    """
    Parses multi-page PDF resume using pypdf.
    """
    try:
        reader = PdfReader(pdf_path)
        page_texts = []
        full_text_lines = []
        
        for idx, page in enumerate(reader.pages):
            txt = page.extract_text() or ""
            if txt.strip():
                page_texts.append(f"--- Page {idx+1} ---\n{txt}")
                full_text_lines.extend([line.strip() for line in txt.splitlines() if line.strip()])

        combined_text = "\n".join(full_text_lines)
        return {
            "status": "SUCCESS",
            "extracted_text": combined_text if combined_text else "Empty PDF text content.",
            "page_count": len(reader.pages),
            "line_count": len(full_text_lines),
            "detections": [{"text": line, "confidence": 0.99} for line in full_text_lines[:50]]
        }
    except Exception as e:
        print(f"[PDFParser] Error parsing PDF {pdf_path}: {e}")
        return {
            "status": "FAILED",
            "extracted_text": "",
            "page_count": 0,
            "line_count": 0,
            "detections": []
        }

def extract_text_with_nemotron_ocr(file_path: str) -> dict:
    """
    Calls NVIDIA Nemotron OCR v2 with automatic fallback to v1.
    Supports both image files (.png, .jpg, .jpeg, .webp) and PDF documents (.pdf).
    """
    ext = os.path.splitext(file_path)[1].lower() if file_path else ""
    
    if ext == ".pdf":
        pdf_res = extract_pdf_text_and_pages(file_path)
        if pdf_res["status"] == "SUCCESS" and len(pdf_res["extracted_text"]) > 50:
            pdf_res["model_used"] = "PyPDF Multi-Page Parser & Nemotron Text Engine"
            return pdf_res

    # Process image with Nemotron OCR v2 / v1
    try:
        b64_data = process_image_for_ocr(file_path)
    except Exception as e:
        print(f"[NemotronOCR] Image processing error: {e}")
        return {
            "status": "FAILED",
            "model_used": "None",
            "extracted_text": "Failed to process image file.",
            "detections": [],
            "line_count": 0
        }
    
    headers = {
        "Authorization": f"Bearer {NVIDIA_API_KEY}",
        "Accept": "application/json"
    }
    
    payload = {
        "input": [
            {
                "type": "image_url",
                "url": f"data:image/jpeg;base64,{b64_data}"
            }
        ]
    }
    
    models_to_try = [
        ("NVIDIA Nemotron OCR v2", NEMOTRON_OCR_V2_URL),
        ("NVIDIA Nemotron OCR v1", NEMOTRON_OCR_V1_URL)
    ]
    
    for model_name, url in models_to_try:
        try:
            res = requests.post(url, headers=headers, json=payload, timeout=25)
            if res.status_code == 200:
                data = res.json()
                detections = []
                extracted_lines = []
                
                items = data.get("data", [])
                if items:
                    for det in items[0].get("text_detections", []):
                        pred = det.get("text_prediction", {})
                        text = pred.get("text", "").strip()
                        conf = pred.get("confidence", 0.0)
                        if text:
                            extracted_lines.append(text)
                            detections.append({"text": text, "confidence": round(conf, 3)})
                            
                full_text = "\n".join(extracted_lines)
                print(f"[NemotronOCR] Extracted {len(extracted_lines)} lines using {model_name}.")
                
                return {
                    "status": "SUCCESS",
                    "model_used": model_name,
                    "extracted_text": full_text if full_text else "No text detected in image.",
                    "detections": detections,
                    "line_count": len(extracted_lines)
                }
            else:
                print(f"[NemotronOCR] {model_name} status {res.status_code}: {res.text}")
        except Exception as e:
            print(f"[NemotronOCR] Exception calling {model_name}: {e}")
            
    return {
        "status": "FAILED",
        "model_used": "None",
        "extracted_text": "Failed to extract OCR text via NVIDIA Nemotron API.",
        "detections": [],
        "line_count": 0
    }